1. Field of the Invention
The present invention relates to a method for producing a conductive film having an electrically conductive property suitable for use as a light-transmitting electromagnetic-shielding film for various display devices, a transparent electrode for various electronic devices, a transparent planar heating element, etc.
2. Description of the Related Art
Recently, a material having a transparent substrate and a mesh-patterned conductive layer of a thin wire of metal or the like has been known as a conductive film having an electrically conductive property suitable for use as a light-transmitting electromagnetic-shielding film for various display devices, a transparent electrode for various electronic devices, a transparent planar heating element, etc. Known methods for producing the material include the following.    (1) Method including the step's of forming a thin copper layer on a transparent substrate by bonding, electroless plating, etc., and etching the thin copper layer into a pattern by photolithography (see Japanese Laid-Open Patent Publication Nos. 05-016281 and 10-163673, etc.)    (2) Method including the steps of arranging ink containing particles of an electroless plating catalyst such as palladium into a pattern on a transparent substrate by printing, and forming a conductive layer thereon by electroless plating (see Japanese Laid-Open Patent Publication Nos. 11-170420 and 2003-318593, etc.)    (3) Method including the steps of exposing a photosensitive silver halide layer formed on a transparent substrate in a pattern to form a patterned developed silver, and forming a patterned conductive layer thereon by plating (see International Publication No. WO01/51276, Japanese Laid-Open Patent Publication No. 2004-221564, etc.)
Among the above three methods, the method of (3) using the silver halide is advantageous in that it contains simpler processes as compared with the photolithography method, can form a thin wire more easily as compared with the printing method, and is suitable for forming a continuous seamless conductive layer. The surface resistance of the conductive film prepared from such a photosensitive material containing a silver salt (particularly a silver halide) can be sufficiently lowered by a smoothing treatment using a calender roll. Furthermore, the method can easily form a metallic silver portion with a desired pattern and uniform shape advantageously, to improve the conductive film productivity (see Japanese Laid-Open Patent Publication No. 2008-251417, etc.)
In a case where a conductive film precursor prepared from a photosensitive material having a silver salt-containing emulsion layer (particularly a conductive film precursor using a long support having a thickness of 95 μm or more) is subjected to a smoothing treatment using a calender roll, deformation defect caused due to wrinkling must be taken into consideration. Japanese Laid-Open Patent Publication No. 2008-251417 describes a combination of a metal roll and a plastic roll capable of preventing the wrinkling.
However, consideration of not only the combination of the metal and plastic rolls but also a force for conveying the conductive film precursor is required in view of preventing the wrinkling.